The present invention relates to filter apparatus, and particularly to a self-cleaning filter which automatically cleans itself after it has accumulated a predetermined quantity of particles filtered from the fluid. The invention is particularly useful for filtering water irrigation systems and is therefore described below with respect to such an application, but it will be appreciated that the invention could advantageously be used in other applications as well.
Irrigation systems commonly include filters for removing foreign particles from the water in order to prevent clogging of the water irrigation devices, such as water sprinklers or drip emitters, connected to the water supply line. It is advantageous in such applications to have the filter clean itself periodically, as required, without either turning off the water, or detaching the filter from the water supply line. One known way for self-cleaning a filter in such applications is by reverse flushing, the filter including a cleaning nozzle which sweeps along and cleans the upstream side of the filter by producing a reverse water flow through the filter. In such known arrangements, the filter is usually provided with means for effecting relative movement between the cleaning nozzle and the filter body during the reverse flushing of the filter, in order to enable the cleaning nozzle to scan the complete surface of the filter body. Such arrangements, however, are quite complicated and expensive to produce and to maintain.
Another known arrangement for self-flushing a filter is to provide a battery of such filters with various valve control arrangements so that certain filters of the battery are used during the normal filtering operation, but upon the accumulation of an undue amount of foreign material within the filter, the valve controls redirect the water to flow through other filters of the battery while the dirtied filters are flushed by reverse flow. Such arrangements are also quite complicated and expensive.
An object of the present invention is to provide a novel form of self-cleaning filter apparatus having advantages in the above respects.